The present invention relates to the coupling of optical components. More particularly, the present invention relates to the alignment of internal optical components and fiberoptic connections of optical devices to avoid signal losses in optical circuits.
Optical communication systems, as well as other optical technologies, require devices that work with optical signals. The best known of such devices is perhaps the ubiquitous silica based optical fiber used for both short and long distance optical transmission. Other well known optical devices include filters, multiplexers, modulators, transmitters, receivers, and power splitters and combiners. The filters and multiplexers are useful in, for example, wavelength division multiplexing (xe2x80x9cWDMxe2x80x9d) systems that have been developed to increase the capacity of optical communication systems by transmitting information at a plurality of differing wavelengths.
Certain characteristics of optical systems, such as the ability to carry considerable information at high speeds over long distances and resistance to electromagnetic interference, make them the technology of choice in many communication applications. Optics, however, also introduce certain complications not present in electronic systems. One complicated area in the optical communications field is the making and breaking of circuitry. Circuitry encompasses conduits, splices, connections and couplings. Typically, copper wire is used as an electronic conduit while fiber and air are used as optical conduits. Splices are semi-permanent junctions of conduits. Connections are temporary junctions between conduits. Couplings join three or more conduits. In electronic systems, splices, connections and couplings are easily made and losses in signals at wire junctions are often negligible because xe2x80x9celectricity travels around cornersxe2x80x9d to follow a conducting path. In contrast, optical splices, connections and couplings are complicated, require care to make, and contribute measurable signal loss to a circuit. This is because light travels in straight lines. Careful engineering is required for light to be gently steered and redirected.
Moreover, unlike electronic systems wherein the orientation of junctions is generally unimportant, direction and alignment of junctions in optical systems is critical. Because the core of an optical fiber has a small diameter, and because optical fibers have a relatively narrow acceptance angle within which light is accepted, a light source must be carefully aligned with a receiving fiber in order to avoid junction losses. Similarly, if a fiber is not carefully aligned so that all emerging light falls onto the light-sensitive area of a detector, some light is lost and sensitivity is reduced. Other alignment issues exist in optical systems. For instance, certain lenses and other devices such as the WDM surfaces discussed below, work best when light passing through them is at nearly normal incidence.
Fiber alignment problems are appreciated in the art and substantial efforts have been made to address them. For two-fiber junctions, efficient splicing may be accomplished with sophisticated fusion splices that automatically align the fibers, and with various mechanical splices, such as capillary splices and v-groove splices. Efficient two-fiber connections use connector bodies with coaxial ferrules that align the fibers and that are mated by concentric, precision sleeves. Fused fiber and planar waveguide couplings are unitary couplings that have no internal alignment issues. Other, more elaborate couplings, especially those that incorporate bulk optic devices, require precise internal alignment in the presence of slight variations in the fabrication of piece parts.
Proper alignment of optical couplings has been given extensive consideration. U.S. Pat. No. 4,435,037 shows a light emitting diode mounted on a movable post within a housing in juxtaposition to the end of an optical fiber centered within a channel in a connector housing. The optical fiber is stationary whereas the post supporting the light emitting diode is moved by a probe inserted through multiple aligning ports until the diode is properly positioned for optimum light coupling into the fiber. U.S. Pat. No. 4,296,998 discloses adjustably positioning an optical fiber relative to a light source to optimize the light output at the end of the fiber and locking the fiber in position within an aperture. U.S. Pat. Nos. 4,135,779 and 4,103,154 disclose the coupling of a pair of optical fibers to a third optical fiber. U.S. Pat. No. 5,535,297 discloses a method of permanently deforming a housing to align a light source and an optical fiber.
U.S. Pat. No. 3,938,895 discloses a method for positioning an optical fiber that involves the passing of light through the optical fiber, detecting the output therefrom through the use of a detector and moving the optical fiber to achieve a desired relationship to the position detector. U.S. Pat. No. 4,989,940 shows a method and apparatus for aligning an optical fiber about a ball and socket support based on a four-gradient measuring device. U.S. Pat. No. 5,745,624 discloses an open loop search process that utilizes signal strength feedback to control the operation of a three-axis stage to position an optical fiber.
Even as these and other efforts progress, more elaborate couplings continue to be developed. For example, optical devices combining bulk optic devices with four or more fibers are in use and are extremely difficult to align. Accordingly, a system for simply and inexpensively aligning fiber optic couplings incorporating bulk optic devices and multiple fibers is required.
The present invention provides a method and apparatus for providing internal alignment of light pathways in an optical device. In accordance with the present invention, an optical steering device is provided for aligning first and second light paths. A first optical element has the first light path which is directed towards the second optical element. The second optical element, which may be rotatable, has the second light path which is directed towards the first optical element. An adjustable steering assembly, which may include a rotatable optical wedge or a ball joint, is used to align the first and second light paths.
In one embodiment of the invention, an optical system includes an optical assembly and a wavelength division multiplexer surface for transmitting a light beam. An adjustable steering assembly is located between this optical assembly and the wavelength division multiplexing surface to align them.
In another embodiment of the invention, an optical amplifier device has a first housing supporting a first optical element which defines a first light path, and a second housing supporting a second optical element which defines a second light path. An adjustable element is located between the first and second housings for changing the direction of the first light path to cause it to align with the second light path.
The invention includes a method of making a multiple optical fiber device, including a first step of transmitting a first light beam along a first direction (or path) through a first optical element, a second step of adjusting the position of a steering assembly to change the direction of the first light beam, and a third step of transmitting the light beam through a second optical element.
The invention also includes a method of operating an optical amplifier device. First, a pump laser is transmitted through a first housing along a first light path. Second, a modulated communication signal is transmitted through a second housing along a second light path. Third, the direction of light propagated through the optical amplifier device is changed to align the first and second light paths. Fourth, the pump laser beam and the modulated communication signal are multiplexed to amplify the modulated communication signal.